1. Field of the Invention
The present invention relates to a side-view light emitting diode (LED) having an LED window opened to a side to emit light sideward. More particularly, the present invention relates to a side-view LED having an improved sidewall reflection structure, thereby enhancing light efficiency and heat release efficiency.
2. Description of the Related Art
A liquid crystal device (LCD) mounted in monitors, mobile phones and Personal Digital Assistants (PDAs) requires external light due to absence of its own light source. Besides, the LCD generally employs a backlight device as a lighting device. The backlight device illuminates the LCD from the back, using Cold Cathode Fluorescent Lamp (CCFL) and Light Emitting Diode (LED) as a light source.
Meanwhile, the backlight device mounted in a small LCD for e.g., mobile phones and PDAs adopt a side-view LED as a light source. Such a side-view LED has an LED window opened to a side to emit light sideward and typically mounted in a backlight device as shown in FIG. 1.
Referring to FIG. 1, the backlight device 50 has a flat light guide plate 54 formed on a substrate 52. Also, a plurality of side-view LEDs 1 (only one LED illustrated) are arrayed on a side of the light guide plate 54. Light L incident onto the light guide plate 54 from the LEDs is reflected upward by a reflective sheet 56 from a micro dot pattern formed on the light guide plate 54. Then the light L exits from the light guide plate 54 to provide a back light to a liquid panel 58 over the light guide panel 54.
FIG. 2 is a front view illustrating an example of a conventional LED 1 as shown in FIG. 1. FIG. 3 is a cross-sectional view cut along the line of FIG. 2.
Referring to FIGS. 2 and 3, the LED 1 includes a package body 10, a pair of lead frames 20 and 22 disposed inside the package body 10 and an LED chip 30 disposed on the lead frames 20.
The package body 10 typically fabricated by molding a high reflective resin is divided into a front part 10a and a rear part 10b with respect to the lead frames 20 and 22. In the front part 10a, a concave 12 and a wall 14 defining the concave 12 are formed. The concave 12 is flat in bottom and widened upwards, as in FIG. 3 so that it is shaped as V or U having a flat bottom (cut in half vertically). The concave 12 is designed to direct light generated from the LED chip 30 along an arrow A direction of FIG. 3. Due to such a concave 12, the wall 14 is narrowed along the arrow A direction, and an inner surface 16 of the wall 14 is inclined.
Also, a transparent encapsulant 40 is filled in the concave 12 to seal the LED chip 30 from the outside. The encapsulant 40 may contain fluorescent material for converting light or ultraviolet ray generated in the LED chip 30 into e.g., white light.
The LED chip 30 is electrically connected to the lead frames 20 and 22 by wires W. In addition, the lead frames 20 and 22 have some portions thereof extending outside the package body 10 to form external terminals.
The conventional LED 1 is accompanied by drawbacks as follows.
The package body 10 is made of a material having a reflectivity of substantially 75%. That is, when light generated from the LED chip 30 is reflected on the inner surface 16 of the wall 14, some considerable portion of the light is absorbed therein, and other portion of the light transmits the wall 14. Disadvantageously, this reduces an amount of light irradiated from the LED 10 forward, i.e., in an arrow A direction.
Also, light absorbed in the inner surface 16 of the wall 14, or light absorbed during its transmission of the wall 14 is converted into heat, thereby increasing temperature of the wall 14. Such thermal conversion of light occurs especially intensively on the inner surface 16 of the wall 14. Consequently this raises temperature of the inner surface 16 and its surrounding area, i.e., the wall 14 and the transparent encapsulant 40. This adversely affects the wall 14, particularly the transparent encapsulant 40.
To overcome problems of the conventional side-view LED, side-view LEDs shown in FIGS. 4 to 6 were proposed. FIG. 4 is a front view illustrating other example of the conventional side-view LED. FIG. 5 is a cross-sectional view cut along the line V-V of FIG. 4. In addition, FIG. 6 is an exploded view of FIG. 5.
As shown in FIGS. 4 to 6, a pair of reflective members 18a and 18b are installed around a concave 12 of a side-view LED 1, i.e., on an inner surface of a side wall 14. These reflective members 18a and 18b are made of a thinly plated high reflective metal. The reflective members 18a and 18b installed allow light generated from the LED chip 30 to be reflected forward in an arrow A direction, thereby enhancing light efficiency of the LED 1. Moreover, this produces heat release effects due to light not absorbed in the inner surface of the wall 14.
However, such a reflection structure entails following drawbacks. The thinly plated reflective members 18a and 18b are hardly installable in the narrow concave 12. Also, in order to be attached to the inner surface of the wall 14, the reflective members 18a and 18b should be shifted in an arrow B direction of FIG. 6 to be adhered and/or compressed. This potentially mars not only the wall 14 but also the LED chip 30, wires W and even reflective members 18a and 18b. 
Furthermore, the reflective members 18a and 18b, which contact the lead frames 20 and 22, cannot be formed in a single structure. That is, the reflective members 18a and 18b should be spaced apart from each other at a predetermined distance G. This augments the number of parts and components and complicates work process. In addition, the conventional side-view LED experiences decrease in reflective efficiency due to light absorbed in the gap G.